No, it won't smell like pee. Mercedes-Benz's new Bluetec diesel technology uses urea--derived from urine--to neutralize particulate emissions and make its GL320 and E320 Bluetec models the cleanest diesels in the world and fifty-state legal in the States. The urea solution must be replenished during normal maintenance stops, but there's no word yet on a rumored do-it-yourself kit based around a compact urinal. The 2007 E320 Bluetec is expected to attain 35 mpg combined fuel economy and goes on sale in the fall of 2006. The GL320 Bluetec and Grand Cherokee Bluetec will attain 25 mpg and are expected in early 2007. Chrysler also announced that a hybrid Bluetec SUV will go on sale in the near future.